1. Field of the Invention
This disclosure relates to the field of water purification and converting wastewater into potable water. In particular, to the use of supercritical water oxidation to purify water to a potable state.
2. Description of the Related Art
The provision of clean drinking water is a problem the world over. In industrialized areas, the provision of clean drinking water and disposal of wastewater is generally done in two steps and often by two completely different agencies.
Water from the environment is generally not accepted as potable. Environmental water is generally purified and cleaned prior to being provided to users with the water being filtered generally multiple times and then treated with chemicals or other processes to destroy microorganisms and remove harmful chemicals. The water may also need to be desalinated to remove salt. This is performed by various water purification plants.
Pollution is introduced into potable water through industrial processes, human wastes, and many other activities where water comes into contact with particular pollutants. In most cases, it is necessary to remove some if not all of these pollutants before the water is returned to the environment. This is performed by various wastewater treatment and sewage treatment plants.
Overall this process essentially results in a near perfect pattern of water recycling. Water is taken from the environment and cleaned for use by humans making it potable in most cases. The water is used and then cleaned for return to the environment where it is “stored” until needed again.
While this type of dual process makes a lot of sense for a large industrialized city and the world as a whole, in many situations the large scale treatment of water is simply not required or may not be economically feasible. This is particularly true in small towns or in temporary residences such as refugee camps, military base camps, or onboard ships.
In these situations, the amount of water available is often a limited amount based on the population and/or location and the available environmental water is regularly insufficient to handle the need. Further, because infrastructure may not be available or may not be functioning, systems are often required to provide emergency relief. Because of this, returning the used water to the environment and gathering environmental water is often not possible and wastewater may be treated and filtered and returned to active use in a relatively short period of time.
While these uses of water can be considered small in terms of quantity, they can still require tens of thousands of gallons of water a day to be consumed and tens of thousands of gallons of wastewater to be generated. Current water purification systems generally require huge amounts of power to run purification systems, pumps, and filters to recycle wastewater with a quick turnaround. Further, many of the most effective purification strategies require one thing that these types of self contained environments do not have, which is time for the wastewater to be treated.
To deal with this problem, most so-called self-contained systems are not self-contained at all but rely on a steady influx of environmental water (and a steady outflow of wastewater) or have a large supply of water available compared to the daily usage demands to allow for the passage of time while water is being purified.
One place where the need for water purification is very necessary is the military. Naval vessels often must be self reliant at sea and support the needs of their crew. Further, ground based units will generally need a base camp or other location to meet the needs of the soldiers which can be positioned far from any infrastructure. Further, such infrastructure, even if it does exist, is likely to be non-functional because of the military activity and contamination concerns can be heightened during military actions as poisoning or fouling of water supplies can be used to slow or halt a military forces' progress. Water sources generally consist of local streams, ponds, and/or brackish water wells. Water purification is also necessary for treating the output water of many human activities. Kitchens, showers, latrines, and laundry services all need potable water to function without danger. All these devices also produce contaminated wastewater that needs to be dealt with to reduce the spread of disease and other dangers.
Currently, the logistics requirements for water in the military are immense. Even when water sources are available to troops in the field, the power demands to pump and purify water and to filter waste and dispose of the contaminants can be enormous. Most existing systems also rely on separate logistics to dispose of solid waste generated by the filtering process. Most of these systems also rely on the burning of diesel or other fossil fuels to generate power which is also polluting and can further increase logistics trails and cost to purify water. Fuel consumption associated with the logistics trail is the predominant cost factor of the overall process, and fuel cost is dictated by the distance traveled to deliver it. For these reasons the ability to process water locally, whether from a water source or wastewater, is a highly sought after operational capability.
The most recent and considered best water purification systems treat water by screening, coagulation, micro-filtration, reverse osmosis, and chlorine disinfection. Additionally, ion exchange and activated carbon may used when the source of water is known to be contaminated with bio-chemical threats. While reverse osmosis is the technology of choice to process “raw” water, the process still has major limitations in the presence of certain contaminants like oil, fuel, silt, algae and viruses, and depending on the contamination, the “raw” water may not be able to be processed to a potable level. Furthermore, reverse osmosis only recovers a portion of the processed water for potable use. The remainder comes out as a brine solution which requires proper disposal. The use of granulated carbon in addition to reverse osmosis can be used to improve potability, but demands that the carbon column be maintained at very strict time intervals in order to ensure that safe potable water levels are met. The addition of calcium hypochlorite to the reverse osmosis treatment may also improve the water product, but certain biological agents are known to be chlorine resistant.
This entire purification system is costly, requires significant supervision, and is still not a particularly high efficiency process. Because of this, water purification is often a costly, cumbersome, and expensive process.